I bought a drop checker and reference solution off of [Ebay Link Removed] I just tested the solution and it came out to 3 kh. This is very irritating. Mabye my test kit is wrong. Im not sure it is just the tetra test so not the most accurate in the world. Im to lazy to make more solution and I dont really want to retest because I dont have a large amount of solution. A 3 kh solution would change color at a lower c02 level right? Does anyone have any reference as to the ppm associated with color change with a 3 kh solution? Im running 6bps into a rex grigg reactor with most of it getting mixed into solution occasionally a bubble will escaped the reactor so not 100 percent efficiency. This is on a 90 gallon tank with a 30 gallon sump with minimal splashing.